The present invention relates generally to the field of sugar processing. More particularly, it concerns an improved process for sucrose inversion.
Sucrose is a disaccharide of glucose and fructose and can be readily extracted from sugarcane (Saccharum spp.) and sugar beet (Beta vulgaris) to provide a nutritive sweetener for use in the production of soft drinks, candies, baked goods, and other foodstuffs for which sweetening is desired. For certain production processes, aqueous solutions of a sweetener such as sucrose are desired. However, aqueous solutions of sucrose used directly after extraction from sugarcane or sugar beet have a number of undesirable properties. First, the maximum sucrose concentration of an aqueous sucrose solution is only about 65 wt %, meaning for every 65 kg of sucrose, the solution contains about 35 kg of water. Attempting to concentrate sucrose to a greater extent leads to crystallization of the sucrose and concomitant difficulty in handling and processing. As can be readily seen, further concentration of the solids would allow a greater mass of solids to be transported per unit volume. Second, aqueous sucrose solutions directly after extraction may contain relatively high levels of ash (non-organic ions), which are generally undesirable for inclusion in sweet foodstuffs.
Sucrose inversion is the process of converting sucrose to its component saccharides, glucose and fructose. The term “inversion” comes from the observation that an aqueous solution containing free glucose and fructose, alone or in combination with residual sucrose, will have different optical properties relative to an aqueous solution containing only sucrose when exposed to polarized light. An aqueous solution containing sucrose, glucose, and fructose, which may be referred to herein as an “inverted sucrose solution,” can be concentrated to a higher level than can an aqueous solution consisting essentially of sucrose; for example, at about 50% inversion, an inverted sucrose solution can be concentrated to about 75 wt % without crystallization. Depending on the inversion percentage, even higher concentrations are possible; for example, honey, which typically contains about 85 wt % total fructose and glucose on a dry solids basis (d.s.b.) and about 1 wt % sucrose d.s.b, also typically has a solids concentration of about 85 wt % without crystallization.
Known inversion techniques include the use of invertase enzyme, which is found in nature in bees, yeast, and bacteria, to catalyze the process, or the use of favorable conditions of pH and temperature, such as the addition of an acid to an aqueous sucrose solution and maintenance of the solution at an elevated temperature or contact of an aqueous sucrose solution with an appropriate ion exchange resin bed. At present, contact of an aqueous sucrose solution with an appropriate ion exchange resin bed is generally held to provide the most convenient and inexpensive technique for sucrose inversion, as it can both invert sucrose without the expense of purifying invertase enzyme and remove ash from the solution, in contrast to addition of an acid, which tends to add ash to the solution.
Although sucrose inversion by use of an ion exchange resin represents the current state of the art, room for improvement exists. The ion exchange resin's active sites are consumed during sucrose inversion, and although the active sites can be regenerated, regeneration requires the unit to go off-line and be treated with concentrated acid and base solutions, which require careful disposal. Also, a side reaction of sucrose inversion produces hydroxymethylfuran (HMF), a bitter-tasting molecule which is not desirable for inclusion in a material intended for use in a sweet foodstuff.
Therefore, it would be desirable to have improved techniques for sucrose inversion by use of an ion exchange resin.